Project Summary. This is a resubmission of a competing continuation application (5 RO1 DA14296;Reaching and Motivating Change in Teen Marijuana Smokers) originally submitted November 2008 in response to NIDA's Behavioral and Integrative Treatment Development Program (PA-07-111). The goal of this trial is to evaluate the efficacy of an enhanced Teen Marijuana Check-Up protocol to reach and intervene with non- treatment seeking adolescents who use marijuana heavily. Two hundred fifty adolescents who use marijuana heavily will receive a 2-session individual motivational enhancement therapy. All participants will also be offered the opportunity, over a 12-month period, to repeatedly reinitiate marijuana counseling. Participants will be randomly assigned to receive one of two types of periodic follow-up contacts: Motivational interviewing- based Marijuana Check-Ins (MCI) or Educational Feedback Control (EFC) sessions. All participants will be reassessed at the 3, 6, 9, 12, and 15-month anniversaries of enrollment. Following their initial motivational enhancement therapy, the 125 experimental condition participants will additionally have a motivational enhancement treatment check-in session with their counselor at the 4, 7, and 10-month anniversaries of enrollment intended to reinforce the maintenance of treatment gains and motivate continued success, increase motivation to change for participants who did not meet their marijuana use goals, and/or prompt utilization of cognitive-behavioral treatment (CBT) sessions as needed. The 125 comparison participants will receive marijuana education at the same time intervals to serve as an attentional control. The experimental condition's rationale is based on: A) findings from our current trial that demonstrated MET feedback sessions showed clear efficacy in fostering reductions in marijuana use and associated consequences at a 3-month follow-up, B) the effects of the intervention were no longer evident at a 12-month follow-up, C) utilization of additional cognitive behavior therapy was minimal but potentially helpful and D) recent research demonstrating the efficacy of continuing care check-up sessions in prompting treatment reengagement by participants who failed to benefit from counseling. The specific aims are: (1) to enhance the effects of the TMCU MET intervention by developing and implementing periodic marijuana check-ins (MCI) over a 9-month period following the initial intervention; (2) to assess whether the MET/MCI approach results in greater reductions in marijuana use and increased treatment engagement than an MET/Educational condition, (3) to assess whether greater utilization of the CBT therapy sessions by MCI condition participants partially mediates the effect on frequency of marijuana use and other outcomes, and (4) to examine other potential mediators, including self-efficacy, perceived descriptive norms, and cost/benefit analyses, of the effect of the intervention on marijuana use outcomes. An enhanced model of intervening with adolescents that promotes marijuana behavior change, the maintenance of such change and prompts the individual to engage in counseling when needed, will likely extend behavior change outcomes in adolescents who would otherwise go untreated. PUBLIC HEALTH RELEVANCE: Project Narrative. Marijuana continues to be the most common illicit drug used by adolescents. Early and frequent marijuana use in adolescence is associated with a host of health and psychological consequences. Two national epidemiological surveys conducted 10 years apart indicate that the prevalence of DSM-IV marijuana abuse and dependence diagnoses has significantly increased despite rates of past year use having remained stable. Treatment admissions for primary marijuana abuse have more than doubled between 1993 (7%) and 2003 (16%). Given that the great majority of adults with one or more marijuana use disorder symptoms report they began smoking before age 18, early intervention efforts with adolescents, particularly those who are using heavily, becomes an important public health objective in order to prevent later problems.